Calcium oxide or hydroxide to improve the charge acceptance of electrographic dielectric resins

Abstract

The charge accepting capacity of electrographic dielectric coatings is improved by dispersing in an organic solvent-soluble thermoplastic insulating resin having carboxyl functionality providing an acid value of from 5-100, from 0.05-3% by weight of calcium oxide or calcium hydroxide.

I claim: 
     
       1. A resin solution adapted to deposit, upon drying, an electrographic dielectric coating having improved charge accepting capacity comprising, in volatile organic solvent solution, an organic solvent-soluble thermoplastic insulating resin having carboxyl functionality providing an acid value of from 5-100, and calcium oxide or calcium hydroxide dispersed in the resin solution in an amount of from 0.05-3% of the weight of the carboxyl-functional resin. 
     
     
       2. A resin solution as recited in claim 1 in which a mineral filler is included in the solution to cause a deposited coating to possess a rough surface. 
     
     
       3. A resin solution as recited in claim 2 in which said mineral filler comprises clay or lithopone and is used in a pigment to binder ratio of from 1:1 to 4:1. 
     
     
       4. A resin solution as recited in claim 1 in which the organic solvent component of the solution comprises xylene or toluene and at least 3% of the weight of said resin of an alcohol to improve the clarity of the solution. 
     
     
       5. A resin solution as recited in claim 4 in which said alcohol contains up to 6 carbon atoms and is used in an amount up to about 100% of the weight of said resin. 
     
     
       6. A resin solution as recited in claim 5 in which said alcohol is selected from ethyl alcohol, propyl alcohol, butyl alcohol, and 2-ethoxy ethanol, and is used in an amount of from 5-30%. 
     
     
       7. A resin solution as recited in claim 1 in which said thermoplastic resin is a solution copolymer of monoethylenically unsaturated monomers containing at least 85% of monomers in which the ##STR2## group is the sole reactive group, and from 0.5-10% of monoethylenic carboxylic acid. 
     
     
       8. A resin solution as recited in claim 7 in which said monomers contain only carbon, hydrogen and oxygen. 
     
     
       9. A resin solution as recited in claim 8 in which calcium hydroxide is used in an amount of from 0.1-2%, and the acid value is from 10-80. 
     
     
       10. A resin solution as recited in claim 9 in which the monoethylenic carboxylic acid is selected from acrylic acid, methacrylic acid, crotonic acid, maleic acid and itaconic acid and provides an acid value of from 20-50, and a monohydric alcohol or ether alcohol containing up to 6 carbon atoms is present in the solvent solution in an amount of from 5% to 100% of the weight of the copolymer. 
     
     
       11. A resin solution as recited in claim 10 in which said resin is a solution copolymer of monoethylenically unsaturated monomers containing only carbon, hydrogen and oxygen, at least 90% of the monomers having the ##STR3## group as the sole reactive group, and from 1.0-8% of monomers being monoethylenic carboxylic acid. 
     
     
       12. A resin solution as recited in claim 11 in which said calcium oxide or calcium hydroxide is present in an amount of from 0.1-2%.